#include <iostream>
#include <algorithm>
#include <cstring>

const int N = 510;
int g[N][N];
int dist[N];
bool st[N];
int n, m;
using namespace std;

int prim()
{
    memset(dist, 0x3f, sizeof(dist));

    int res = 0;
    for (int i = 0; i < n; ++i)
    {
        int t = -1;
        for (int j = 1; j <= n; ++j)
        {
            if (!st[j] && (t == - 1 || dist[t] > dist[j]))
            {
                t = j;
            }
        }

        if (i && dist[t] == 0x3f3f3f3f)
        {
            return 0x3f3f3f3f;
        }

        if (i)
        {
            res += dist[t];
        }
        st[t] = true;
        for (int j = 1; j <= n; ++j)
        {
            dist[j] = min(dist[j], g[t][j]);
        }
    }
    return res;
}
int main()
{
    cin >> n >> m;
    memset(g, 0x3f, sizeof(g));
    while (m--)
    {
        int a, b, c;
        scanf("%d%d %d", &a, &b, &c);
        g[a][b] = g[b][a] = min(g[a][b], c);
    }

    int t = prim();
    if (t == 0x3f3f3f3f)
    {
        printf("impossible");
    }
    else
    {
        printf("%d", t);
    }
    return 0;
}